• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.4
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• pp.288-292
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• 2006

Through statistically designed experiments, lysis agents were optimized to effectively disrupt bacterial cells in a microfluidic device. Most surfactants caused the efficient lysis of Gram-positive microbes, but not of Gram-negative bacteria. A Plackett-Burman design was used to select the components that increase the efficiency of the lysis of the Gram-negative bacteria Escherichia coli. Using this experimental design, both lysozyme and benzalkonium chloride were shown to significantly increase the cell lysis efficiency, and ATP was extracted in proportion to the lysis efficiency. Benzalkonium chloride affected the cell membrane physically, while lysozyme destroyed the cell wall, and the amount of ATP extracted increased through the synergistic interaction of these two components. The two-factor response-surface design method was used to determine the optimum concentrations of lysozyme and benzalkonium chloride, which were found to be 202 and 99 ppm, respectively. The lysis effect was further verified by microscopic observations in the microchannels. These results indicate that Gram-negative cells can be lysed efficiently in a microfluidic device, thereby allowing the rapid detection of bacterial cells using a bioluminescence-based assay of the released ATP.

• Korean Journal of Veterinary Research
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• v.50 no.4
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• pp.279-284
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• 2010

Combination therapy of antibiotics is leading to improved efficacy or safety profiles with decrease emergence of bacterial resistance. Because of this benefit, many of antibacterial combinations have been used in veterinary practice for the past few decades. The purpose of this study was to examine the in vitro activity of an amoxicillin alone and in combination with other antibiotics against pathogenic bacteria of fish origin. Based on the fractional inhibitory concentration (FIC) index (FIC $$\leq_-$$ 0.5), a synergistic interaction was shown in combination of florfenicol with amoxicillin or cefuroxime. The combination of florfenicol and amoxillin showed higher antibacterial activity than that of florfenicol and cefuroxime. Ratio of amoxicillin and florfenicol in combination was 1 : 1, which showed the antibacterial activity against bacterial isolates of fish as compared with other ratios. A synergetic effect of the combination (amoxicillin and florfenicol) was further confirmed in the time-kill curve study. The study showed a better in vitro antibacterial activity of a 1 : 1 combination of amoxicillin and florfenicol than the individual antibacterial against bacterial isolates of fish. In conclusion, the combination of florfenicol and amoxicillin may serve as a potential antibacterial therapy in fishes infected pathogenic bacteria.

• Microbiology and Biotechnology Letters
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• v.47 no.2
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• pp.303-309
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• 2019

Earlier studies by our group revealed that gallic acid in phytochemicals stimulated biofilm production in epiphytes, while caffeic acid in phytochemicals inhibited biofilm production in non-epiphytes. It is well documented that antimicrobial secretion by some epiphytic bacteria inhibits non-epiphytic bacterial growth on leaf surfaces. These selection criteria help plants choose their microbial inhabitants. Calcium and iron in phytochemicals also stimulate biofilm formation and thus, may be selection criteria adopted by plants with respect to their native epiphytic population. Furthermore, the processing of leaves during phytochemical extraction impacts the composition of the extract, and therefore its ability to affect bacterial biofilm formation. Computation of the Hurst exponent using biofilm thickness data obtained from the Ellipsometry of Brewster Angle Microscopic (BAM) images is an efficient tool for understanding the impact of phytochemicals on epiphytic and non-epiphytic populations when compared to fluorescent microscopy, scanning electron microscopy, and staining techniques. To the best of our knowledge, this is the first report that uses the Hurst exponent to elucidate the mechanism involved in plant microbe interaction.

• Journal of Digestive Cancer Research
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• v.10 no.1
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• pp.31-38
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• 2022

Ulcerative colitis (UC) exhibits chronic intestinal inflammatory conditions with cycles of relapse and remission. The incidence is rapidly growing in Asian countries including South Korea possibly due to changes in lifestyles. Although the etiology of inflammatory bowel disease is inconclusive, gut microbiota composition is considered a critical factor involved in the pathogenesis of UC. The overgrowth of pathogenic bacteria evokes hyper-immune responses in gut epithelium causing tissue inflammation and damage. Also, failure to regulate gut epithelium integrity due to chronic inflammation and mucus depletion accelerates bacterial translocation aggravating immune dysregulation. Gut microbiota composition responds to the diet in a very rapid manner. Epidemiological studies have indicated that the risk of UC is associated with low plant foods/high animal foods consumption. Several bacterial strains consistently found depleted in UC patients use plant food-originated dietary fiber producing short chain fatty acids to maintain epithelial integrity. These bacteria also use mucus layer mucin to keep gut microbiota diversity. These studies partly explain the association between dietary modification of gut microbiota in UC development. Further human intervention trials are required to allow the use of specific bacterial strains in the management of UC.

• Journal of Microbiology and Biotechnology
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• v.26 no.8
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• pp.1439-1445
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• 2016

A yellow, rod-shaped, non-motile, gram-negative, and strictly aerobic bacterial strain, designated LPB0005^T, was isolated from a marine gastropod, Reichia luteostoma. Here the genome sequence was determined, which comprised 3,395,737 bp with 2,962 protein-coding genes. The DNA G+C content was 36.3 mol%. The 16S rRNA gene sequence analysis indicated that the isolate represents a novel genus and species in the family Flavobacteriaceae, with relatively low sequence similarities to other closely related genera. The isolate showed chemotaxonomic properties within the range reported for the family Flavobacteriaceae, but possesses many physiological and biochemical characteristics that distinguished it from species in the closely related genera Ulvibacter, Jejudonia, and Aureitalea. Based on phylogenetic, phenotypic, and genomic analyses, strain LPB0005^T represents a novel genus and species, for which the name Cochleicola gelatinilyticus gen. nov., sp. nov. is proposed. The type strain is LPB0005^T (= KACC 18693^T = JCM 31218^T).

• The Plant Pathology Journal
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• v.40 no.3
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• pp.299-309
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• 2024

The rice blast disease, caused by the fungal pathogen, Magnaporthe oryzae (syn. Pyricularia oryzae), poses a significant threat to the global rice production. Understanding how this disease impacts the plant's microbial communities is crucial for gaining insights into host-pathogen interactions. In this study, we investigated the changes in communities of bacterial and fungal endophytes inhabiting different compartments in healthy and diseased plants. We found that both alpha and beta diversities of endophytic communities do not change significantly by the pathogen infection. Rather, the type of plant compartment appeared to be the main driver of endophytic community structures. Although the overall structure seemed to be consistent between healthy and diseased plants, our analysis of differentially abundant taxa revealed the specific bacterial and fungal operational taxonomic units that exhibited enrichment in the root and leaf compartments of infected plants. These findings suggest that endophyte communities are robust to the changes at the early stage of pathogen infection, and that some of endophytes enriched in infected plants might have roles in the defense against the pathogen.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.261-261
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• 2006

Membranes are a central feature of all biological systems and their ability to control many cellular processes is critically important. As a result, a better understanding of how molecules bind to biological membranes is an active area of research. In this report, the interaction between our biomimetic structures and different biological membranes is reported using both model vesicle and in vitro bacterial cell experiments. These results show that lipid composition is more important for selectivity than overall net charge. An effort is made to connect model vesicle studies with in vitro data and naturally occurring lipid compositions.

• Toxicological Research
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• v.13 no.1_2
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• pp.111-116
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• 1997

In the present study, we investigated the neutralization activity of various antimicrobials against lipopolysaccharide (LPS) as well as interaction between two antimicrobials (enrofioxacin and coilstin) using checkerboard method. The neutralization activity of antimicrobials used in the test was assayed by means of LAL chromogenic test after reaction of LPS with colistin, enorfioxacin, ampicillin, polymyxin B, oxytetracycline, streptomycin, and erythromycin. As the results, the neutralization activity of coltstin and polymixin B had a more stronger than that of tested other antimicrobials. In bacterial culture broth, the best neutralization activity of the antibiotics was also shown to coltstin and polymixin B. Meanwhile, It was shown to have synergism between enorfloxacin and coltstin on the basts of FIC (fractional inhibition concentration). The FIC of enorfioxacin-colistin combinations was 0.50-1.03 to Staphylococcus aureus R-209, 1.03-1.06 to Salmonella typhimurium, 0.75-1.25 to Bordetella Bronchtseptica and 1.02-1.25 to E. coli K88ab. On the basts of the above results, the present study may be of clinical usefulness in the choice of an antibiotic therapy for severe sepsts in animals.

• BMB Reports
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• v.38 no.1
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• pp.97-103
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• 2005

Under the condition of expression of $\lambda$ P protein at lethal level, the oriC DNA-binding activity is significantly affected in wild-type E. coli but not in the rpl mutant. In purified system, the $\lambda$ P protein inhibits the binding of both oriC DNA and ATP to the wild-type DnaA protein but not to the rpl DnaA protein. We conclude that the $\lambda$ P protein inhibits the binding of oriC DNA and ATP to the wild-type DnaA protein, which causes the inhibition of host DNA synthesis initiation that ultimately leads to bacterial death. A possible beneficial effect of this interaction of $\lambda$ P protein with E. coli DNA initiator protein DnaA for phage DNA replication has been proposed.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2410-2414
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• 2008

Human heart valves diseased by congenital heart defects, rheumatic fever, bacterial infection, cancer may cause stenosis or insufficiency in the valves. Treatment may be with medication but often involves valve repair or replacement (insertion of an artificial heart valve). Bileaflet mechanical heart valves (BMHVs) are widely implanted to replace the diseased heart valves, but still suffer from complications such as hemolysis, platelet activation, tissue overgrowth and device failure. These complications are closely related to both flow characteristics through the valves and leaflet dynamics. In this study, the physiological flow interacting with the moving leaflets in a bileaflet mechanical heart valve (BMHV) is simulated with a strongly coupled implicit fluid-structure interaction (FSI) method which is newly organized based on the Arbitrary-Lagrangian-Eulerian (ALE) approach and the dynamic mesh method (remeshing) in FLUENT. The simulated results are in good agreement with previous experimental studies. This study shows the applicability of the present FSI model to the complicated physics interacting between fluid flow and moving boundary.